The field of art to which this invention pertains is mobile aerial towers, and more particularly such towers for maintenance vehicles.
Mobile aerial towers of various types have been used for a variety of purposes in maintenance vehicles, a primary objective of which is to maximize the maneuvering capability of the aerial tower and associated work platform or cab so as to provide access to overhead power lines, street lamps, upper stories in fire fighting equipment, and to levels well below the vehicle support surface for various purposes, among other applications.
Various constructions have been proposed and used heretofore, including turntable mounted elevatable telescopic boom type towers, knuckle-boom types in which a secondary boom is mounted for selected pivotal movement from a vertical "up" to vertical "down" position in relation to the remote end of an elevatable primary turntable mounted boom, combinations of telescopic and knuckle-boom towers, and combinations of primary and secondary booms in which the secondary boom may be actuated as on a trolley means lengthwise of the primary boom and elevatable relative thereto. It is common practice in such prior aerial towers to provide means for maintaining a work platform or operator's cab in a fixed level relationship irrespective of the combinations of maneuvers available to the booms and related elements of the aerial tower.
A principal object of the present invention is to provide an improved combination of aerial tower elements which increases the available maneuverability thereof.